Philae lander ‘falls sleep’

The Philae lander performed about 56 hours of continuous scientific measurements on the surface of Comet 67P, but by 01:15 CET on 15 November the energy state of the lander became so low that the engineers assumed that Philae would go into sleep mode during the night. “Philae is a complete success,” said Project Manager Stephan Ulamec of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). From around 23:30 CET, Philae was in contact with the Lander Control Center (LCC) at DLR Cologne and sent back scientific data from the SD2 drill and the COSAC instrument. At the beginning of the contact period, engineers in the DLR LCC continued to send commands to Philae. The lander performed well, although the radio link to Earth failed several times. The mission scientists cheered repeatedly as new data arrived from space.

During the night, the lander also conducted measurements with the PTOLEMY instrument, acquired two images with the ROLIS camera and examined the interior of the comet nucleus using radio signals – together with the CONSERT instrument on board the Rosetta orbiter. In addition, the LCC team was able to rotate the body of the lander with its solar panels by 35 degrees, so that they are better oriented towards the Sun. The LCC team hopes that this will allow the lander batteries to charge faster in its shaded location. Philae’s hibernation means a break for the team in the LCC: “After a very exciting and successful week, Philae is now taking the time to rest – and the team is now able to take a breath,” said DLR engineer Koen Geurts. In recent days, the LCC had been working around the clock to command the lander and make optimal use of the time available for the ‘First Science Sequence’.